1. Field of the Invention
The present invention relates to card like electronic equipment or device that is detachably connectable to host equipment, such as a personal computer, and more particularly, to an apparatus and method for controlling access to contents protected by, for example, copyright, or kept in secrecy, and stored in the card like electronic equipment, such as an IC memory card.
2. Discussion of the Related Art
Typically, detachable card like electronic equipment, such as an IC memory card, is used to store and reproduce contents data to a host data processing device, such as a personal computer (PC) in order to transmit or receive the contents data protected by, for example, copyright, along with keeping security protection.
In general, the IC memory card includes a central processing unit (CPU) for controlling operations in the IC memory card, a read only memory (ROM) for storing identification (ID) for permitting the usage of the IC memory card, a random access memory (RAM) for storing a password for permitting access to the contents data in the IC memory card, and a clock for providing time data in the IC memory card.
Usually, in order to maintain the protection of a right or the security of contents data, it is possible for the password to designate a limited permission period, e.g., an expiration time, for using the contents in the IC memory card. For increasing the security of the protected contents, conventionally, the usage of the password is controlled by time data provided from the built-in clock in the IC memory card. Thus, when the password is stored in the IC memory card, in general, both the registration date or the renewal date of the password and an expiration date for permission of the password are preliminarily designated in host equipment, such as a personal computer (PC).
When the IC memory card is installed in the host equipment, e.g., a PC, an interrupt process in the IC memory card detects a present time by reading the time data counted in the clock at predetermined time intervals. Further, both of a previous renewal time of the password and a registered time of the password are read out. The detected present time is compared to the read out renewal time.
If the present time has exceeded the designated time period of the renewal time of the password, the usage of the password is no longer permitted since the password has already expired relative to the designated permission time period. Accordingly, a warning regarding expiration of the permission for the password is, for example, displayed on the PC.
However, in the conventional IC memory card system, there is no measurement for protecting the password data or the altering of the time data. Thus, there is no protection for keeping the security of the password data itself, nor for time data that is provided from the built-in clock in the IC memory card. As explained above, in the conventional IC memory card, the password is stored in the RAM. Usually, the password is read out by executing an enciphered program that is stored in the ROM in the IC memory card. Accordingly, if the enciphered program in the ROM has unlawfully been accessed, it becomes possible to easily acquire or steal the password data stored in the IC memory card system.
Further, it is intentionally possible to alter the time data of the clock itself for extending the limited time period. Thus, by unlawfully altering the time of the clock, it becomes possible to change the renewal time for the password.
Such unlawful altering of the time data in the IC memory card generates further problems. Usually, the IC memory card stores application software for trial use or music data as the contents, in order to permit usage of the software along with permitting a certain limited time period. In spite of the permission of the limited period, it is possible to illegally extend the limited period of the trial use of the application software or music data by altering the time data of the clock in the IC memory card. Since music data is usually protected by copyright, such an illegal usage of the contents data in the IC memory card produce serious problems.